JPH02150870A - Developing device - Google Patents

Abstract

PURPOSE:To remove impurities, such as dust and to prevent toner sticking and formation of abnormal images as well as to attain the uniformity of a thin toner layer and the long-term stabilization of images by rotating a developing roller backward for a specified period of time at arbitrary timing. CONSTITUTION:The developing roller 20 of the image forming device having a developing device which forms the thin toner layer by bringing a blade 22 into contact with the roller 20 is rotated backward for a certain specified time only at the arbitrary timing, such as at the standing by when the power of the image forming device is turned on, at the warming up, at the printing or after the end of image forming. The developing roller is rotated backward for the certain period of time at the arbitrary timing after the power of the image forming device is turned on, by which the impurities 24, such as dust, penetrated between the roller 20 and the blade 22 are removed and the sticking of the toner 23 to the blade 22 is prevented. The formation of the abnormal images is prevented as well. The uniform and thin toner layer is formed at all times in this way and the long-term stabilization of the images is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing device used in an image forming apparatus such as a printer, an electrophotographic copying machine, or a facsimile machine.

(Prior Art) As an example of an image forming apparatus, FIG. 7 shows a schematic configuration diagram of a laser printer. Briefly explaining the operation of this printer, the recording paper 2 is fed by a paper feed roller 17 in the direction of the arrow from the paper feed device 1 of the printer main body 10, and is timed by a pair of registration rollers 3 to form a drum-shaped sheet. The latent image carrier is conveyed to a latent image carrier consisting of a photoreceptor 4.

The photoreceptor 4 is rotationally driven in a clockwise direction.

The surface is charged by the charger 5 and irradiated with laser light from the laser optical system 6 to form an electrostatic latent image on the photoreceptor.

This latent image is developed by the developing device i! 7, the toner forms a visible image, this visible image is transferred to the recording paper 2 conveyed to the photoreceptor 4 by a transfer charger 8, and the transferred visible image on the recording paper is fixed by a fixing device 9. be done.

The recording paper that has left the fixing device 9 is then discharged by a paper discharge roller 18 to a discharge section 11 in the direction of arrow B.

On the other hand, residual toner is removed from the photoreceptor 4 after the visible image has been transferred by a cleaning device 13 having a cleaning blade 12 , and the charge is removed by a charge removal brush 14 .

The toner removed from the photoreceptor is collected by a collection roller 16 into a toner collection chamber 15 and stored therein.

In the conventional non-magnetic component developing device 7, as shown in the partially enlarged cross-sectional view of FIG. The toner 23 is tribo-electrified with a certain amount (referred to as a lump amount). This frictionally charged toner removes dust and the like and prevents the toner from sticking as the blade 22 in contact with the developing roller 20 wears out.

Here, the positively or negatively charged toner is
It adheres to the developing roller, is carried to the photoreceptor 4, and visualizes the latent image on the photoreceptor. In order to maintain a balance between the photoreceptor potential and the toner potential, the developing roller 20 and the replenishing roller 21 are set to a positive or negative potential as a bias.

(Problem to be Solved by the Invention) When the developing roller 20 and blade 22 portion (Fig. 8) is enlarged, as shown in Fig. 9 (1), the blade 22
The toner 23 is scraped off to form a uniform thin layer of toner on the developing roller 20.

In this case, between the developing roller 20 and the blade 22, the ninth
As shown in Figure (2), when impurities 24 such as dust enter and toner 23 adheres to the blade 22, the thin toner layer at that location becomes uneven, resulting in abnormal images such as white streaks on the image. appear.

In addition, as the blade 22 in contact with the developing roller 20 wears out, impurities such as dust 24 are removed and toner 23 is prevented from sticking, so impurities such as dust are removed between the developing roller and the blade. There is a problem in that when dirt and other debris invades, it takes time to remove the debris.

The present invention solves the above problems, and by rotating the developing roller in reverse for a certain period of time at any given time, removes impurities such as dust, prevents toner from sticking, prevents abnormal images, and reduces toner thinning. The purpose is to make the layer uniform and stabilize the image for a long time.

(Structure and Operation) In order to achieve the above object, the present invention provides an image forming apparatus having a developing device that forms a thin toner layer by contacting a blade with a developing roller. time, warming up, printing,
It is characterized in that the developing roller is rotated in reverse for a certain period of time at an arbitrary time such as after the completion of image formation.

The present invention removes impurities such as dust stuck between the developing roller and the blade and fixes the toner to the blade by rotating the developing roller in reverse for a certain period of time at any time after the image forming apparatus is powered on. This prevents abnormal images from occurring.

(Embodiment) FIG. 1 is a diagram showing a main motor control circuit for driving a developing roller according to an embodiment of the present invention.

25 is a control unit (μCPU) of a laser printer, for example, which includes a ROM 25B for storing operation programs, a RAM 25C having a work area, an I10 boat 25D for the driver 20D of the main motor 20M for driving the developing port 20, and the I10 boat 25D for controlling these operations. It consists of a controlling CPU 25A. In addition, 26 is the main motor for driving the developing roller (
This is an ON/FF reverse rotation switch for the DC motor) 20M, and is input via the I10 port 25D of the control section.

Further, operations during standby and printing when the laser printer shown in FIG. 7 is powered on will be explained with reference to the flowchart shown in FIG. 2 and the timing chart shown in FIG. 3.

First, we will discuss the standby time when the laser printer is powered on. When the power is turned on (a) shown in FIG. 2(1), the laser printer warms up (b) and becomes ready (Q). And the display (Fig. 1118
), you will be asked if you want to print (d), and if no, check the developing roller reverse rotation (e) subroutine [Figure 2 (
2)].

Therefore, if reverse rotation is unnecessary (No of e).

That is, if there is no abnormal image, the process returns (e) and returns to the ready state (c). If you need reverse rotation here (
If YES), that is, if there is an abnormal image,
The developing roller reverse rotation switch 26 shown in FIG. 1 is turned on, and a reverse rotation instruction signal [FIG. 3 (a)] is input to the CPU 25A via the I10 port 25D of the control section 25.

A reverse rotation time [T seconds in FIG. 3(A)] is set by the ROM 25B and RAM 25C of the control unit 25 (e,), and the main motor 20M for driving the developing roller is started (e,) via the driver 20D. A reverse rotation signal [Figure 3] is given. Then, after T seconds have elapsed (e
4) Stop the main drive motor (e5).

Thereafter, the state returns to the ready state (c) in FIG. 2(1).

Next, we will discuss printing using a laser printer.

From the ready state (c) in Figure 2 (1), a message "Print" is opened on the display (d), and if YES, one page is printed [(a) in Figure 3 (2)]. ), then the developing roller reverse rotation check subroutine [Figure 2 (
2) (e)]. Therefore, reverse rotation is not necessary (No)
If so, a message “Subsequent printing” will be opened on the display (g), and if it is finished, it will return to the ready state [Figure 3 (
2) (a)], if printing is to be continued, one sheet is printed again (f), and the above operation is repeated.

If reverse rotation is required, the subroutine shown in Figure 2 (2) is performed in the same way as when the power is turned on and on standby. ].

Next, the operation during warming up (startup) of the laser printer will be described with reference to the operation flowchart shown in FIG. First, the CPU 25A of the control section 25 is initialized using a power-on reset signal (Sl).

The control unit 25 controls the driver 2 via the I10 boat 25D.
At the same time as turning on the reverse rotation signal for the main drive motor 20M to 0D, the reverse rotation time T is set using the ROM 25B and RAM 25G. As a result, the main driving motor 20M is started, and when the reverse rotation time T has elapsed, an OFF signal for reverse rotation of the motor is inputted to the driver 20D via the I10 boat 25D, and the reverse rotation operation is completed. Next, a signal for forward rotation is input, and a print command is awaited.

This is because the developing roller rotates in reverse for a certain period of time when the laser printer warms up (starts up).

Next, the operation of the laser printer after the image output is completed will be described with reference to the operation flowchart of FIG.

The laser printer prints 1 to N images by turning on the driving main motor 20M in response to a normal motor rotation signal and rotating in the normal direction based on the print command.

Then, when the last paper is detected to be ejected, the developing roller reverse rotation switch 26 is turned ON as described above, and the reverse rotation time (T seconds) is set for a certain period of time using the motor reverse rotation signal, and the main drive motor 20M is turned on. Rotate backwards. T
When the second time has elapsed, the motor reverse rotation signal is turned OFF and the motor is stopped.

As above, turn on the developing roller reverse rotation switch at any time.
By doing so, the developing roller can be rotated in the reverse direction. In this way, as the developing roller rotates in the opposite direction, as shown in FIG.
Impurities such as dirt stuck in between are reliably removed in the direction of the arrow.

Further, since the developing roller rotates in the opposite direction, it is possible to scrape off the toner attached to the blade during the formation of a thin toner layer, thereby preventing the toner from sticking to the blade. As a result, a uniform toner layer is always formed, and abnormal images such as white streaks, which are conventional, do not occur.

(Effects of the Invention) As explained above, the present invention allows impurities such as dust between the developing roller and the blade to be removed by operating the developing roller reverse rotation switch at any time and rotating the developing roller in the reverse direction. It can be removed to restore a normal image.

In addition, since the developing roller rotates in the opposite direction, it is possible to scrape off the toner attached to the blade when forming a thin toner layer, which prevents toner from sticking and always forms a uniform thin layer of toner. This prevents abnormal images such as white streaks from occurring.

Further, the reverse rotation of the developing roller and the forward rotation for the next printing operation are automatically performed by the control section, which has the effect that it does not take much time to remove impurities such as dust.

Further, since the space between the developing roller and the blade is brought to an initial state each time the laser printer warms up or after image output is completed, the above-mentioned effects are more effective.

[Brief explanation of the drawing]

FIG. 1 is a developing roller drive main motor control circuit according to an embodiment of the present invention, FIG. 2 is a flow chart of the operation of the laser printer during standby and printing when the power is turned on, and FIG. 3 is the operation of FIG. 2. Timing chart, Figure 4 is a flowchart of the operation during warming up of the laser printer, Figure 5 is a flowchart of the operation of the laser printer after image output, and Figure 6 explains how to remove dust and prevent toner sticking according to the present invention. 7 is a schematic configuration diagram of a laser printer in which the present invention is implemented, FIG. 8 is a partially enlarged cross-sectional view of the developing roller and blade in FIG. 7, and FIG. 9 is a diagram showing the blade for the conventional developing roller. FIG. 4...Photoreceptor, 7...Developing device, 20...Developing roller, 20M...Main motor for drive, 20
D...Driver, 21...Replenishment roller, 22.
...Blade, 23...Toner 24...Impurities such as dust, 25...Control unit, 25A...CPU
, 25B...ROM, 25C...RAM,
25D...I10 boat, 26...Developing roller reverse rotation switch.

Claims (1)

[Claims] In an image forming apparatus having a developing device that forms a thin layer of toner by contacting a blade with a developing roller, any time such as standby when the image forming apparatus is powered on, warming up, printing, or after image formation is completed. At the time of
A developing device characterized by rotating a developing roller in reverse for a certain period of time.